I think this suggestion will balance lockdown because:
1. Bombers can't do direct damage and being in a situation where everyone has a gun is almost impossible to survive.
2. The only way for a bomber to attack is by rendering their invisibility frames and start to charge a bomb.
3. All bomber's attacks are visible before the actual attack by a couple of seconds because enemies can see the fuse time or even more if you take charge time in account.
4. Bombs' damage is usually the same as a sword strike so charging a bomb isn't nearly as rewarding compared to swinging/charging a sword.
5. This will encourage the use of blast bombs over haze bombs which are considered annoying by almost all lockdown players and invisibility frames discourages using shard bombs.
There are 3 other solutions that will balance bombs (and bomber gear) not only in lockdown but also in the clockworks:
1. Increase the overall damage of all bombs.
2. Decrease the overall charge time of all bombs.
3: Make attack speed increase decrease the fuse time on bombs instead of increasing the animation speed and add that stat on some of the bomber armors.
I would prefer to have the radius remain, but the fuse time be invisible to enemies. If you get your timing down, it won't change too much, however bomb fuses give players a brief moment of "safe time" to approach bombers. Taking that away, they'll need to be more strategic about their approaching, but can stand at the border of the bomb.
Alternatively, introduce the whole "fuse time reduction" thing we've all be clamoring for for a while and make it exclusive to:
A) guardian shield (FTR - low)
B) recon shield (FTR - medium)
C) mad bomber (FTR - medium per piece)
Blam, now you have a neat way to make both mad bomber more viable, but also make lockdown bombing more interesting.